CN102910654A

CN102910654A - Preparation method of fibrous boehmite with large specific surface area and large pore area

Info

Publication number: CN102910654A
Application number: CN2012104459309A
Authority: CN
Inventors: 李振虎; 宋家庆; 徐向宇; 刘玉欣
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2012-11-08
Filing date: 2012-11-08
Publication date: 2013-02-06
Anticipated expiration: 2032-11-08
Also published as: CN102910654B

Abstract

The invention discloses a preparation method of fibrous boehmite with large specific surface area and large pore area, and belongs to the technical field of catalyst carriers. The preparation method comprises the following steps of: preparing a sodium metaaluminate solution firstly, then dropwise adding the sodium metaaluminate solution into an aluminum sulfate solution to obtain a boehmite precursor, ageing, crystallizing, filtering, washing and drying to obtain the fibrous boehmite. The boehmite prepared by the method is fibrous, the diameter of fiber is 2-15nanometers, the specific surface area is more than 300m<2>/g, the pore area is more than 1.0ml/g, the product purity is high, and the stability is good. According to the preparation method, the operation is simple, the environment can not be polluted, raw materials are easy to obtain, and the preparation method has industrial application prospect.

Description

The preparation method of the fibrous boehmite of a kind of bigger serface macropore volume

Technical field

The invention belongs to the support of the catalyst preparing technical field, particularly the preparation method of the fibrous boehmite of a kind of bigger serface macropore volume.

Background technology

γ-Al ₂O ₃Because it has certain surface acidity and higher specific surface area, good thermostability is widely used in carrier, pottery, buffing material and coated material etc. as catalyzer.Boehmite is preparation γ-Al ₂O ₃Important prerequisite, through becoming γ-Al by γ-AlOOH after 400-700 ℃ of roasting ₂O ₃Therefore, the size of control boehmite particle and pattern have played vital effect to the character of aluminum oxide.

Fibrous boehmite is because its special appearance structure makes it with the characteristic of bigger serface and macropore volume, and this all is incomparable for normal thin diaspore and pseudo-boehmite, although pseudo-boehmite has the specific surface area (SA＞400m of super large ²/ g) but because its appearance structure, pore volume is generally about 0.3ml/g.

The method of the fibrous boehmite of preparation has electrochemical process at present, hydrothermal synthesis method, and wherein the method for Hydrothermal Synthesis is divided again and is added organic formwork agent method and aluminum isopropylate hydrolysis method, and these method energy consumptions are higher, and environment is unfriendly, and cost is high.

Mention in the CN102153119A patent and adopt aluminum nitrate as the aluminium source, by adding organic formwork agent (cetyl trimethylammonium bromide, Macrogol 2000, copolymer p 123) etc., volatile salt is prepared diameter 70-500nm as precipitation agent, and length 2-3 μ m specific surface is at 290-380m ²The boehmite of/g, but it adds a lot of expensive organic formwork agents, and production cost is too high, and environmental pollution is large.

Document J.Phys.Chem.C2007,111, the sulfate ion that 103-107(aluminum isopropylate and 2-propyl alcohol prepare in the gel affects the boehmite crystallisation process) report is take aluminum isopropylate and 2-propyl alcohol as raw material, at room temperature adopts sol-gel method to prepare the boehmite precursor, by regulating SO ₄ ^2-Thereby the digestion time of the value of/Al and precursor has been controlled the boehmite crystal of different-shape, and boehmite and the fibrous boehmite of micro capsule pattern arranged, and wherein the specific surface area of fibrous boehmite is 386m ²/ g, pore volume are 1.82cc/g, yet the cost of aluminum isopropylate own is higher, and recycle inconvenience, cause its industrial application technical process complicated, and production cost is high, and environmental pollution is large.

Adopt sodium metaaluminate and Tai-Ace S 150 as raw material among the patent CN102653410, the fibrous boehmite of Hydrothermal Synthesis successfully synthesizes Fibre diameter at the nanometer fibrous boehmite of 5-20nm, and its specific surface area is at 100m ²/ g-249m ²/ g, its production cost is not high, environmental friendliness, but the specific surface area of product is lower.

In above-mentioned document and the patent, synthetic fibrous boehmite fiber is thicker, specific surface area is less, although it is thin that the synthetic boehmite of aluminum isopropylate can obtain Fibre diameter, the boehmite that specific surface area is large, the unavoidable problems such as but its environmental pollution is large, and is with high costs are brought very large difficulty for its suitability for industrialized production.

Summary of the invention

The objective of the invention is for above deficiency, seek out a kind of with low costly, the method for the fibrous boehmite of eco-friendly preparation simultaneously, also will obtain the specific surface area height, the fibrous boehmite that pore volume is large.

Technical scheme of the present invention is: at first prepare sodium aluminate solution, then dropwise be added in the alum liquor, obtain the boehmite precursor, aging, filtration after the crystallization, washing, drying obtain product.

The preparation method's of the fibrous boehmite of bigger serface macropore volume of the present invention concrete steps are:

1) under 100-120 ℃ be that NaOH and the gibbsite of 2-8 is mixed with sodium aluminate solution with mol ratio, the reaction times is 6-24h, and the concentration of sodium metaaluminate is 5-55wt%; The preferred 4-6 of the mol ratio of NaOH and gibbsite;

2) sodium aluminate solution with step 1) preparation dropwise is added drop-wise in the alum liquor that concentration is 0.1-0.7mol/L, to pH be 7-11, stop during preferred 9-10 dripping, stir 10-120min under the room temperature, obtain the boehmite precursor;

3) with the boehmite precursor in 20-80 ℃, preferred 40-60 ℃ lower aging 1-50 hour, preferred 2-4 hour;

4) continue at 80-200 ℃, preferred 90-120 ℃ lower crystallization 5-100 hour, preferred 8-24 hour;

5) filtration, washing, drying obtain product.

The prepared boehmite of present method is fibrous, Fibre diameter 2-15 nanometer, and specific surface area is greater than 300m ²/ g, pore volume are greater than 1.0ml/g, and product purity is high, good stability.This preparation method is simple to operate, is easy to control, and is free from environmental pollution, and raw material is cheap is easy to get, and has prospects for commercial application.

Description of drawings

Fig. 1 is the x-ray diffraction spectra of the fibrous boehmite of bigger serface macropore volume that obtains among the embodiment 1.

Fig. 2 is the transmission electron microscope photo of the fibrous boehmite of bigger serface macropore volume that obtains among the embodiment 1.

Embodiment

Below the present invention will be described in detail by specific embodiment, but the present invention is not restricted to following embodiment.

Pattern and the grain size of boehmite are measured by high-resolution-ration transmission electric-lens.

Used NaOH, Al in following examples and the Comparative Examples ₂(SO ₄) ₃.18H ₂O and gibbsite are all available from the Beijing Chemical Plant.

Embodiment 1

Get the 15.0g gibbsite (Chalco Shanxi Aluminium Plant product, alumina content 65wt%, lower with), 35.5g sodium hydroxide (Beijing Chemical Plant's product, analytical pure, lower with), 50.5g deionized water and stirring evenly rear 120 ℃ of reaction 5h is prepared sodium aluminate solution; Then dropwise be added drop-wise in the alum liquor that concentration is 0.4mol/L, be to stop in 9.3 o'clock dripping to the pH value, stirring at room is after half an hour, in 60 ℃ aging 2 hours, then slurries are transferred in the stainless steel cauldron of inner liner polytetrafluoroethylene, changed over to 120 ℃ of crystallization 8h of baking oven; Filter after taking out, with 60 ℃ of dryings behind the deionized water washing and filtering, obtain sample S1.

Product is carried out materialization to be characterized: specific surface area and the pore volume of measuring this product are listed in table 1.

By XRD spectra as can be known, synthetic product is boehmite.

Embodiment 2

Get the 12.0g gibbsite, 40.0g sodium hydroxide, 50.0g deionized water and stirring evenly rear 110 ℃ of reaction 5h is prepared sodium aluminate solution; Then dropwise be added drop-wise in the alum liquor that concentration is 0.5mol/L, be to stop in 9.1 o'clock dripping to the pH value, stirring at room is after half an hour, in 40 ℃ aging 3 hours, then slurries are transferred in the stainless steel cauldron of inner liner polytetrafluoroethylene, changed over to 110 ℃ of crystallization 24h of baking oven; Filter after taking out, with 60 ℃ of dryings behind the deionized water washing and filtering, obtain sample S2.

By XRD spectra as can be known, synthetic product is boehmite.

Embodiment 3

Get the 9.0g gibbsite, 25.0g sodium hydroxide, 60.0g deionized water and stirring evenly rear 115 ℃ of reaction 5h is prepared sodium aluminate solution; Then dropwise be added drop-wise in the alum liquor that concentration is 0.4mol/L, be to stop in 9.9 o'clock dripping to the pH value, stirring at room is after half an hour, in 60 ℃ aging 4 hours, then slurries are transferred in the stainless steel cauldron of inner liner polytetrafluoroethylene, changed over to 90 ℃ of crystallization 24h of baking oven; Filter after taking out, with 60 ℃ of dryings behind the deionized water washing and filtering, obtain sample S3.

By XRD spectra as can be known, synthetic product is boehmite.

Embodiment 4

Get the 10.0g gibbsite, 41.0g sodium hydroxide, 50.0g deionized water and stirring evenly rear 120 ℃ of reaction 5h is prepared sodium aluminate solution; Then dropwise be added drop-wise in the alum liquor that concentration is 0.2mol/L, be to stop in 9.9 o'clock dripping to the pH value, stirring at room is after half an hour, in 60 ℃ aging 4 hours, then slurries are transferred in the stainless steel cauldron of inner liner polytetrafluoroethylene, changed over to 90 ℃ of crystallization 18h of baking oven; Filter after taking out, with 60 ℃ of dryings behind the deionized water washing and filtering, obtain sample S4.

By XRD spectra as can be known, synthetic product is boehmite.

Embodiment 5

Get the 13.6g gibbsite, 35.7g sodium hydroxide, 50.0g deionized water and stirring evenly rear 100 ℃ of reaction 5h is prepared sodium aluminate solution; Then dropwise be added drop-wise in the alum liquor that concentration is 0.7mol/L, be to stop in 9.7 o'clock dripping to the pH value, stirring at room is after half an hour, in 60 ℃ aging 4 hours, then slurries are transferred in the stainless steel cauldron of inner liner polytetrafluoroethylene, changed over to 90 ℃ of crystallization 12h of baking oven; Filter after taking out, with 60 ℃ of dryings behind the deionized water washing and filtering, obtain sample S5.

By XRD spectra as can be known, synthetic product is boehmite.

Embodiment 6

Get the 12.0g gibbsite, 40.0g sodium hydroxide, 50.0g deionized water and stirring evenly rear 115 ℃ of reaction 5h is prepared sodium aluminate solution; Then dropwise be added drop-wise in the alum liquor that concentration is 0.1mol/L, be to stop in 9.7 o'clock dripping to the pH value, stirring at room is after half an hour, in 60 ℃ aging 3 hours, then slurries are transferred in the stainless steel cauldron of inner liner polytetrafluoroethylene, changed over to 90 ℃ of crystallization 12h of baking oven; Filter after taking out, with 60 ℃ of dryings behind the deionized water washing and filtering, obtain sample S6.

Comparative Examples 1

According to document Langmuir2007,23,9850-9859 mixes aluminum nitrate and sodium hydroxide solution under 80 ℃, and keeps stirring 2h, cleans with deionized water and precipitates, and then adds the PEO template, Al (OH) ₃And H ₂The molar ratio of O and PEO is: 0.05:0.02:0.8, and 100 ℃ of lower hydro-thermals two days, behind the deionized water wash product, 80 ℃ of lower oven dry obtain boehmite R.

Table 1

Sample	BET specific surface area (m ²/g)	Pore volume (ml/g)
			S1	301	1.01
S2	306	1.02
			S3	330	1.20
S4	360	1.18
			S5	368	1.11
S6	459	1.60
			R	165	0.45

Claims

1. the preparation method of the fibrous boehmite of bigger serface macropore volume is characterized in that, its concrete preparation process is:

1) under 100-120 ℃ be that NaOH and the gibbsite of 2-8 is mixed with sodium aluminate solution with mol ratio, the reaction times is 6-24h, and the concentration of sodium metaaluminate is 5-55wt%;

2) sodium aluminate solution with the step 1) preparation dropwise is added drop-wise in the alum liquor that concentration is 0.1-0.7mol/L, stops to drip when pH is 7-11, stirs 10-120min under the room temperature, obtains the boehmite precursor;

3) the boehmite precursor is lower aging 1-50 hour in 20-80 ℃;

4) continue at 80-200 ℃ of lower crystallization 5-100 hour;

5) filtration, washing, drying obtain product.

2. preparation method according to claim 1 is characterized in that, the mol ratio of the described NaOH of step 1) and gibbsite is 4-6.

3. preparation method according to claim 1 is characterized in that step 2) described pH is 9-10.

4. preparation method according to claim 1 is characterized in that, the described temperature of step 3) is 40-60 ℃.

5. preparation method according to claim 1 is characterized in that, the described digestion time of step 3) is 2-4 hour.

6. preparation method according to claim 1 is characterized in that, the described temperature of step 4) is 90-120 ℃.

7. preparation method according to claim 1 is characterized in that, the described crystallization time of step 1) is 8-24 hour.